Cretaceous/Paleogene Boundary Events in the Gulf Coast: Comparisons between Texas and Alabama
Malcoilm Hart, Andres Cardenas, and Peter Harries
Following identification of the Chicxulub crater on the Yucatan Peninsula, the Cretaceous/Paleogene boundary sections in the Gulf Coastal plain were recognised as being of international significance. Malcolm Hart and colleagues have investigated the successions in Texas from 2009-2012, and comparable localities in Alabama have now been studied and sampled for micropaleontology. Sections on Highway 263 near Braggs, Mussel Creek and Moscow landing appear to have been deposited in shallower water environments as compared to the Brazos River area, Texas. The sequence of events is still, however, relatively simple to identify and there are many similarities. The Braggs section is often regarded as the 'type' section, but is - in reality - rather atypical. Above the erosion surface at the tope of the Prairie Bluff Fm most of the mudstones and carbonate-rich beds are flat lying, and very similar to the other two successions. In the Mussel Creek and Moscow Landing sections, however, there are a number of hiatues, erosion surfaces, burrowed horizons, lignite beds, conglomeratic beds and channels. The single, brown, sandstone-rich, spherule-rich bed also contains shell fragments and rounded reworked clasts of Prairie Bluff Fm. In the Brazos River area there is also only one spherule-rich horizon and the eroded topography in which it sits is comparable to the succession at Moscow landing and in the construction site of Miller's Ferry. Previous work appears has either attempted to disprove an end-Cretaceous impact, or shoe-horned the succession into a sequence stratigraphic model that may not be a correct interpretation of the sea level changes at the K/Pg boundary. Most authors have also used a variety of versions of the boundary and not adhered to the 'official' ICS definition.
AAPG Search and Discovery Article #90167©2013 GCAGS and GCSSEPM 63rd Annual Convention, New Orleans, Louisiana, October 6-8, 2013